Hand Deflection Reaction

The arm deviation reaction (ARM) is a reflexive deviation to the side not under the influence of external irritation, but arising spontaneously during rapid passive extension of the arms, returning the shoulder and forearm from a flexion position. Described in 1952 by English neurologist Peter Blacker.

The hand deviation reaction is a phenomenon of cognitive psychology, a phenomenon of visual perception. The history of its study goes back more than two centuries, but scientists still cannot give it an unambiguous explanation. Researchers in this area are divided by the lack of consensus regarding the reasons for detecting the reaction of a deviating hand. The phenomenon was described in 1804 by the Italian scientist Silvio Ernst Lanza in a monograph entitled “The Hand Pointing While Standing and Sitting” (Le braccia indicano nel posizionamento e nel sedersi). It is noteworthy that he also introduced the term, which is now known to the entire scientific community. But let's take a closer look at this phenomenon:

The reaction of a deviating (moving) hand is a strange ability of our consciousness to notice everything that is beyond our bodily perception. Many psychologists attribute this reaction to the ability to learn or remember, more precisely, to spatial memory. This ability is especially clearly expressed in figure problems. This means that, looking at the line dividing the straight fingers of an outstretched hand, the observer may make a mistake and mistakenly take the left or right shoulder blade, kneecap or ankle, or something else along the contour line of the hand as the base of the straight line - that is, the center of the phalanges index, middle and ring fingers. The cause of the error, as psychologists note, is the incorrect interpretation of our brain data. That is, our brain receives information from the eyes about the direction of the lines, and then analyzes the data about each hand simultaneously, along with the direction of the hand lines and other factors. Taken together, if this analysis scheme is triggered at the initial stage, which happens at small angles, which are called acute, the illusion of movement of the elements of the figure arises, which in fact do not exist. This phenomenon was discovered by academician A.R. Luria and is called the otan phenomenon. Despite many studies aimed at studying this ability, there is still no precise explanation for the hand deviation reaction, as well as its practical application. However, unlike many other mysteries, this feature of the nervous system plays an important role in human life, and therefore it is given due attention.